The effect of large-area pulsed electron beam melting on the corrosion and microstructure of a Ti6Al4V alloy

Abstract

The use of titanium alloys in biomedical applications continues to increase due to the excellent stiffness to weight ratio and high corrosion resistance. In order to improve the surface wettability and corrosion properties of a Ti--6Al--4V alloy, the surface treatment method, large area electron beam melting technique was investigated. Polished samples were subject to pulsed treatments of 1, 15 and 25 at 1.38 J/cm 2 beam energy. Surface roughness and contact wetting angles were reduced as a result of the treatment. Microstructural analysis of the surface by XRD and FIB--TEM revealed a martensitic alpha prime phase formed as a result of the high cooling rates induced by the treatment. The presence of this homogenous martensite layer was shown to facilitate a compact passive oxide layer formation during corrosion, thus improving corrosion rates by several orders of magnitude compared to an untreated sample. Large area electron beam melting of Ti--6Al--4V induced a number of changes to the near surface microstructure of the samples, all of which could be used to tailor mechanical and corrosion properties to that of a desired application, without compromising the bulk material properties. These are explored in detail in this work.

Surface modification of structural material for nuclear applications by electron beam melting: enhancement of microstructural and corrosion properties of Inconel 617

“…The lowering of the passivation current density is clearly indicating the improved passivation tendency of the EB treated material. While we suspect surface purification after high energy electron beam irradiation due to selective ablation for commonly observed impurities in the base material, we believe microstructural refinement to have a greater bearing on the corrosion performance [42,43]. Furthermore, it also possible that EB melting is leading to redistribution and homogenization of alloying elements which in turn could reduce the galvanic coupling tendency of the alloying elements with respect to the matrix.…”

Various categories of defects after surface alloying induced by high current pulsed electron beam irradiation

“…The pulsed melting is capable to dissolve second-phase particles, and the fast (10 8 -10 9 K/s) quenching from liquid state leads to the formation of up to 10 m melted layer of non-equilibrium structure-phase states in the surface layers [5,6]; while the ultra-fast solidification results in the formation of a structure containing solid solutions, nanosized second-phase segregates and amorphous-phase particles [4,[7][8][9]. Due to its ultra-rapid thermal cycles, the treatment of HCPEB was mostly used to increase the hardness [10], wear [11] and corrosion resistance [12][13][14]. What's more, it could be wildly use in biomedical application [15,16].…”

Human Skeletal Stem Cell Response to Multiscale Topography Induced by Large Area Electron Beam Irradiation Surface Treatment

“…Large Area pulsed Electron Beam irradiation (LAEB) is a novel method to create metal surface layer modifications (Proskurovsky et al, 1998 ; Walker et al, 2014 ). The known benefits of LAEB treatment include: (i) improvement of Ti alloys fatigue characteristics (HCEI, 2015 ), (ii) enhancement of material strength properties (Proskurovsky et al, 2000 ), (iii) nano-hardening of the surface and sub-surface with resultant increased resistance to initiation and propagation of cracks (Gao, 2013 ), and (iv) improvement in the surface corrosion resistance (Walker et al, 2014 ). However, to date, there has not been any published experimental work exploring the biological potential of LAEB-induced alterations of surface topography.…”